Cracking dicyclopentadiene to monomer



Dec. 1, 1970 s. ROBOTA CRACKING DICYCLOPENTADIENE T0 MONOMER Filed Oct. 11, 1968 N H 513% 93: E553 26:58

.5335 35638 M w m I 558m L! 5 0 5028 EEE )6 9:63 IR O 2:38 (2 ZQEZQESE 3 5.52:. 55550635 United States Patent 3,544,644 CRACKING DICYCLOPENTADIENE T0 MONOMER Stephen Robota, North Tonawanda, N.Y., assignor to Hooker Chemical Corporation, Niagara Falls, N.Y., a corporation of New York Filed Oct. 11, 1968, Ser. No. 766,695 Int. Cl. G07c 3/40 US. Cl. 260-666 7 Claims ABSTRACT OF THE DISCLOSURE In the liquid phase cracking of dicyclopentadiene, a partial condenser is employed wherein the cracked gaseous mixture is held for a short time prior to being directed to a fractionating column.

BACKGROUND OF THE INVENTION ing column. It has been found that a short residence time of the cracked gaseous mixture in a partial condenser sub-" stantially decreases the resin buildup and consequently resulting in an improved yield.

In US. Pat. 2,831,904 there is described a liquid phase cracking of dicyclopentadiene. The improvement described in this patent is the use of an auxiliary liquid, which has a paraflinic hydrocarbon fraction having an initial boiling point above 250 C. and of which at least 80% boils within a range of no greater than about 50 C., lying within the range between 250 C. and about 350 C., and which permits a decrease in resin buildup and the plugging of mechanical systems.

Another method for cracking dicyclopentadiene is the hot tube process wherein dicyclopentadiene is funneled through a heated tube to obtain a pure product. An example of such a process in US. Pat. 2,582,920. However, the hot tube process is used mainly in the laboratory and is not readily amenable to commercial operations primarily because of plugging of the tube after continuous processing. In the patent, there is no discussion of retention time of the cracked gaseous mixture in a partial condenser.

It is an object of this invention to obtain an improved yield in the cracking of dicyclopentadiene and to obtain a pure product.

It is also an object to obtain a continuous process for the cracking of dicyclopentadiene. These and other objects of this invention will become evident as the invention is further described below.

SUMMARY OF THE INVENTION Dicyclopentadiene may be cracked to relatively pure monomer in a hydrocarbon oil. As the gaseous mixture is emitted from the cracking chamber, it is directed to a partial condenser. The residence time in a partial condenser may range from 1 to about 8 seconds. As the gaseous mixture leaves the partial condenser, it is directed to a fractionation column from which pure monomer is obtained.

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PREFERRED EMBODIMENTS OF THE INVENTION Crude dicyclopentadiene may be employed. However, it is preferred to use relatively pure dicyclopentadiene. The resulting monomer from the process of this invention is pure monocyclopentadiene. A lower limit of crude dicyclopentadiene would be one that contains approximately dicyclopentadiene, With purity preferred.

Various hydrocarbon oils may be employed as solvents. It is preferred that the oil not be reactive at the operating temperatures and further that it be stable to dicyclo and monocyclopentadiene. The oils that may be employed in this process may be aromatic or paraflinic, with the latter being preferred. The parafiinic oils that may be employed are those that have an initial boiling point of about 250 C. to about 350 C. and wherein 80% of the oil will boil off in approximately 20 to about C. above the initial boiling point. The characteristics of an oil can be tested according to ASTM test D86-61. A preferred parafiinic oil is one that has an initial boiling point of 270 C. to approximately 350 C. and 80% of which will boil over at approximately 20 to about 75 C. above the initial boiling point. It is also desirable to have a paraflinic hydrocarbon oil that will be stable to continuous processing. This can be determined by periodically testing the pour point of the oil as it is recycled. Pour point of about -30 C. to about 15 C. may be employed, preferably about --20 C. to about 10 C.

The cracking temperatures may range from approximately 250 C. to about 350 C., preferably 280 C. to about 320 C. As the gaseous mixture leaves the cracking chamber, it enters the partial condenser which may be maintained at approximately 45 C. to about 100 C., preferably approximately 45 C. to about 70 C. The inlet to the fractionation apparatus should be maintained at a high enough temperature to keep the monocyclopentadiene' in the vapor state and low enough to remove the high boiling impurities such as, dicyclopentadiene or other polymers of cyclopentadiene.

The inlet to the fractionation apparatus may be maintained at about 45 C. to about 70 C., preferably about 45 C. to about 65 C. The fractionation apparatus itself may be kept at about 40 C.

The cracked gases referred to in this invention are those gases leaving the cracking chamber. They are generally comprised of cyclopentadiene, hydrocarbon oil and a small amount, if any, of dicyclopentadiene. The function of the partial condenser is to condense the hydrocarbon oil which oil will then run down the inside of the condenser back to the cracking chamber. Since the partial condenser is kept relatively cool, high boiling polymers of cyclopentadiene will also be condensed and returned to the cracking chamber.

The cracking chamber for commercial operation may employ a stainless steel vessel, a glass lined vessel or some other ceramic vessel.

The partial condenser may be made of carbon steel, a glass lined vessel or other materials obvious to one of skill in the art.

The residence time in the partial condenser should be short about 1 to about 8 seconds, preferably 5 to about 7.0 seconds and more preferably about 6.6 seconds. Residence times of less than about 5 seconds are not preferred for they may require expensive refrigeration equipment.

The fractionation column is usually packed with ceramic packing while the column itself may use glass-lined or nickel walls. The column may also be packed with ceramic berl saddles of varying length, such as inch or glass helices of varying lengths such as inch or 1 inch.

In order to obtain improved yields of cyclopentadiene, it

3 is desirable that the condensed vapors be cooled as quickly as possible. cyclopentadiene has a tendency to repolymerize which is an exothermic reaction. The purified monocyclopentadiene should be cooled rapidly in a zone having a temperature from C. to minus 40 C. The formation of dimer can also be prevented by immediately reacting ,monocyclopentadiene. An example of such a process is described in Belgian Pat. 498,176 wherein monocyclopentadiene is reacted with acetylene to form bicyclo (2,2,1)-2,5-heptadiene. Also cyclopentadiene is a highly useful intermediate which can be employed to produce such compounds as chlorinated cyclopentadiene, such as chlorendic acid.

This process can be further described by an analysis of the schematicdiagram attached. Dicyclopentadiene from dicyclopentadiene reserve 1 is directed to the cracking chamber 7 through line 5. The auxiliary liquid is also di-. rected from auxiliary liquid reserve 2 to the cracking chamber through line 6. Metering pumps 3 and 4 are employed in order to maintain a constant level of material in the cracking chamber. The materials may be preheated prior to being added to the cracking chamber. They may also be merged together before being added to the crack- I ing chamber. T o insure further a constant amount of material in the cracking chamber an overflow vessel 18 is employed. Material from this verflow vessel may be directed back to the cracking chamber. During the cracking process, the auxiliary liquid will reflux to coat the partial condenser thereby preventing repolymerization of the cyclopentadiene. The gaseous mixture that leaves the crack ing chamber is directed to partial condenser 9 wherein it has a short retention time as it continues to the fractionation column 13. In order to cool and condense the gases in the partial condenser, liquid from cooling liquid reserve 11 pass into the condenser through line 12 and exit back to the reserve through line 10. The cyclopentadiene gas is directed tothe fractionation column 13 from the partial condenserand as it exits in the liquid form it can either be stored or passed on for further processing 14.

The use of a liquid phase cracking system lends itself to the continuous process of cracking dicyclopentadiene. As the pure product is removed from the auxiliary liquid, said liquid can be recycled and used again. The limiting factors are the amount of resin buildup and the point at which the auxiliary liquid becomes clogged with impurities. A

quick test for determining the adequacy of the liquid is by measuring the pour point as has been described above.

Varying weight ratios of dicyclopentadiene to paraflinic oil may be used from about 1:1 to 15:1, preferably 4:1

to :1 and even more preferably 10:1 -(dicyclopentathe scope of the invention as described above.

EXAMPLE 1 Retention time in partial condenser of seconds or more A paraflinic oil having an initial boiling point of 330 C. and 80% of which boiled over at about 357 C. and

having a specific gravity at room temperature of 0.835 was employed. Charged to a 1000 ml. flask is 400 ml. (334 grams) of the oil. The oil was agitated and heated to 310 C. At this temperature the oil expanded to 500 ml. Heated dicyclopentadiene of 95% purity-was fed to the cracker at various rates up to 3.22 grams per minute. The feed is a dicyclopentadiene oil mixture in a weight ratio of 10 to 1 (dicyclo:oil). The spent oil was continuously discharged by an overflow line to maintain a 500 ml. oil volume in the cracker. This experiment was run continuously. Two sample runs are indicated in Table I. The percent take oif of product is 70%. The series was plagued by resin buildup in the exit vapor lines and other pieces of equipment.

TABLE I.ORACKING OFDICYCLOPENTADIENE USING A PARAFFINIC OIL Run No 1 2 Retention time in partial condenser, seconds 15. 6 l8. 5 Dicyelopentadiene teed:

Grams (as dicyclopentadiene) 567 442 Grams/minute (as dicyclopentadiene) 2. 91 2. 45 Cracker liquid volume, ml- 500 500 Cracker vapor volume, mL- 500 500 Duration of run, minutes 195 177 Cracker temperatures:

Oil (liquid), avg., C 305 308 (vapor), avg, C 282 282 Fractionation system temperature:

Inlet to fractionation column (avg.), 0-. 47 48 Reflux (avg), C 41. 5 41 Oil discharged from- Cracker (grams) 66. 5 36. 2 Pour point of sample, C -23 -23 Product collected:

Specific gravity at 20 C- 8060 8056 Percent cyclopentadiene. 98. 6 98. 5 Grams 433. 5 372 Recovery (product/feed X 100) percent' 76. 5 84-. 1 Partial condenser volume, ml 450 450 The product recovery averaged 82.3% for all operating runs.

EXAMPLE 2 Retention time in partial condenser of 5 seconds Similar equipment and materials are employed in this example as in Example 1 except that the partial condenser retention time in this example is about five seconds. This was achieved by using a partial condenser with a volume of 150 ml. The feed is a dicyclopentadiene: oil mixture of 10: 1 by weight. The cyclopentadiene product purity was 99.9% plus. Table II describes the operating data. The percent of product take-0E is TABLE IL-CBACKING OF DICYCLOPENTADIENE USING PARAFFINIC OIL AND A PARTIAL CONDENSER RETEN- TION TIME OF 5 SECONDS Run No 1 2 Retention time in partial condenser 5. 0 5, 1 I Dicvclopentadiene teed:

Grams (as dicyclopentadiene) 434 437 Grams/minute (as dyclopentadlene) 3. 09 2. 91 Cracker liquid volume, ml. 500 500 Cracker vapor volume, ml. 500 600 Duration of run, minutes-- Cracker temperatures:

Oil (liquid), avg. C 305 305 (vapor), avg. C 294 296 Fractionating system temperature:

Inlet to fractionation column (avg), C 66 66 Reflux (avg), C 40 40 Oil discharged from cracker:

Grams 67, 5

Pour point of sample, C -35 -36 Product collected:

Specific gravity at 20 C 8019 8023 Percent cyclopentadiene 100. 0 100. 0

Gram: 4131. 5 431. 0

Recovery (product/teed X 100) percent 99. 3 98. 5

Pour points were taken on previous runs wlthout changing oil. The average product recovery for all runs is 95.5%.

What is claimed is:

1. A method of cracking dicyclopentadiene to monocyclopentadiene comprising heating the dicyclopentadiene in a hydrocarbon solvent at a temperature in the range of 250 C. to about 350 0., partially condensing the cracked gaseous mixture leaving the cracking chamber by retaining the gaseous mixture in a condenser for. 1 to about 8 seconds and recovering substantially pure monocyclopentadiene by distillation.

2. The method of claim 1 wherein the cracking is conducted at a temperature of from 275 C. to about 350 C.

3. The method of claim 1 wherein the retention time is from about 5 to about 7 seconds.

4. The method of claim 1 wherein the retention time is about 6.6 seconds and recovery of monocyclopentadiene is by means of fractional distillation.

5. The method of claim 1 wherein the recovering is by means of fractional distillation.

6. The method of claim 2 wherein the hydrocarbon solvent has an initial boiling point of about 250 C. to about 350 C., and 80% of which boils over according to ASTM test D86-61 at 20 to about 100 C. higher than the initial boiling point.

7. The method of claim 1 wherein a continuous process 6 solvent to the cracking chamber and continuously recovering substantially pure monocyclopentadiene.

References Cited UNITED STATES PATENTS DELBERT E. GANTZ, Primary Examiner operates by continuously adding dicyclopentadiene and 10 OKEEFE, Assistant EXamiller 

